Glycerin may be obtained as a by-product from the transesterification of triglycerides (i.e., biodiesel fuel production) in an amount as high as about 11 percent of the overall products formed. Recent advances made in biodiesel fuel production have encouraged the development of many new industrial applications that use glycerin. For example, glycerin can be used as a raw material in the industrial production of propylene glycol, epichlorohydrin, acrylic acid, or polyhydroxybutyrate. Glycerin in a pure form also has many uses, such as for example, in pharmaceuticals and cosmetics.
The basic chemical reaction for the catalyzed production of biodiesel fuel is shown in Equation 1 below. In this reaction, a fat or oil (such as soybean oil, rape seed oil, etc.) is reacted with a short chain alcohol in the presence of a catalyst to produce glycerin and compounds capable of being used as biodiesel fuel. The short chain alcohol (ROH), which preferably is methanol or ethanol, is usually used in excess to facilitate a high conversion of oil or fats to biodiesel fuel. The catalysts commonly used are basic in nature and easily dispersible in the alcohol reactant. Examples of such catalysts, include sodium hydroxide, potassium hydroxide, sodium methylate, or the like. As shown in Equation 1, the R′, R″, and R′″ moieties indicate fatty acid chains, such as palmitic, stearic, oleic, and linoleic acids, that are found in naturally occurring oils and fats.

The glycerin formed as a byproduct during the transesterification of triglycerides is normally of a crude or impure grade. The typical impurities found in the glycerin by-product include the catalyst, various soaps, methanol, lipids, and water. Since the catalyst is typically neutralized at the end of the transesterification reaction, the catalyst normally exists in solution as a salt.
Purification is required to transform the crude glycerin to a state suitable for use in existing or emerging applications. The salt content in crude glycerin, which often ranges from 5 percent to 7 percent, makes conventional purification techniques cost intensive. Examples of conventional purification methods include vacuum distillation and bleaching with activated carbon. However, such purifying processes are expensive and the elimination of process steps that require the regeneration or disposal of a consumable material, such as activated carbon, is desirable. Accordingly, there exists a need to provide an improved method and system for purifying glycerin and products obtained therefrom that are more cost effective than conventional methods and systems.